1. Field of the Invention
The present invention generally relates to a push latch device serving to open and close a door of an audio rack and a cover of a control box accommodating a variety of switches in a television set, audio appliances, etc., and more particularly, to a small-sized and inexpensive push latch device capable of operating surely and smoothly.
2. Description of the Prior Art
The push latch device is widely employed for opening and closing the door of the audio rack and the cover for protecting the control box accommodating the variety of switches in the television set and the audio appliances. The push latch device serves to open and close the door simply by pushing the door without pulling it, the arrangement being such that the door is locked by closing and then pushing it and the locking is released by pushing the door once again, thus opening it.
This type of push latch device is constructed in such a way that a slider having hooks at its tip is slidably incorporated into a case formed with an opening at its one end in association with a stoppage mechanism. Directing now attention to FIGS. 12(A) through 12(D), there is shown a one example of the push latch device. FIGS. 12(B) and 12(C) in combination show a state in which side plates of the case are removed.
More specifically, the push latch device is constructed such that a slider c provided with substantially V-shaped hooks b at its tip is incorporated into a case a consisting of a case body a1 formed with an opening extending from its one end to its side surface and of a cover member a2 for covering the one open side surface of the case body a1 so that the slider is slidable in the longitudinal direction of the case 1. A coil spring f spans from a proximal end d of the slider c to a distal end inner surface e to elastically bias the slider c towards the opening formed in the case body a1. A recession h formed in a one side surface g of the slider c accomodates a plate spring i having elastical forces acting in the depthswise direction of the recession h. A spherical body j is placed on the plate spring i so that the spherical body j is arranged to be pushed against an inner surface of the cover member a2 by dint of the plate spring i. An endless guide groove l depicted with an imaginary line in the Figure is chased in the inner surface k of the cover member a2. This endless guide groove l is, as illustrated in FIG. 12(D), constituted by: a rectilinear portion m extending straight from the opening of the case a towards the distal end thereof; a crooked portion n including a substantially V-shaped portion s which is disposed on the side of distal end and extends in continuation to the rectilinear portion m; a short rectilinear portion p continuously leading to the terminal point of the crooked portion n and extending to the mid-point in the direction of the opening formed in the case; and an inclined portion q obliquely extending towards the initial point of the rectilinear portion m. Furthermore, a step is formed at the conjunction between the rectilinear portion m and the crooked portion n for the purpose of preventing a reverse movement of the spherical body j.
When the thus constructed push latch device is practically used, this device is installed in a port of the box such as an audio rack or the like and an arrow-like engagement projection t is fitted to the practical surface of the door. On the occasion of practica1 use, the slider c is slid into the case a by pushing the slider c with the engagement projection t, thereby moving the spherical body j along the guide groove in the direction indicated by an arrowhead in the Figure. In the course of this movement, the spherical body j is seized by the substantially V-shaped stoppage portion s. As illustrated in FIG. 12(C), this permits the slider c to halt in a state wherein the slider is accomodated in the case a.
This type of push latch device is, however, attended with the following problems. It is needed that a depth of the guide groove l be varied by complicatedly undulating the bottom thereof to determine the direction in which the spherical body j moves. The push latch device has disadvantages of being rather costly in production and incapable of miniaturizing the device itself, because it requires a good number of components such as the plate spring i for pushing the spherical body j against the cover member a2. In an as-pressed state, the spherical body j is brought into contact with the guide groove l, and hence the frictional resistance created when the spherical body j moves becomes considerably large. In addition, the operation of the slider c is deteriorated during the practical use in some cases. Lubricants such as grease or the like are required for preventing these undesirable conditions. Moreover, there is a probability to cause the deterioration in operation, when the lubricant is consumed up or solidified.